The present invention relates to a throttle valve control system for opening and closing a throttle valve for use in an automobile by means of an actuator such as a motor or the like.
For an electronically controlled throttle system in which the throttle valve is operated by electronic control, in addition to such a case in which a throttle demand opening is instructed from an engine control system and it operates in response to this instruction, there is another case in which an electronically controlled throttle valve is provided independently of the engine control system for allowing operation by determining a control target position thereof by the electronically controlled throttle system itself. More specifically, there are such cases including: a case for driving its throttle to its close direction or to its open direction in order to learn a minimum position (full close learning) or a maximum position (full open learning); a case for driving its throttle by the steps of reading its acceleration pedal position, obtaining a corresponding throttle opening relative to the value read out from a look-up table or the like; or a case in which the electronically controlled throttle system drives its throttle without instruction from the engine control system when data exchange between the electronically controlled throttle system and the engine control system is interrupted. Because that the engine is driven based on an air flow quantity that is controlled by a throttle opening, and a fuel injection control and an ignition control in which the engine control system is involved, in case where the electronically controlled throttle system itself determines a control target for operation, in order appropriately to execute the fuel injection control, the ignition control and the like, it is necessary for the electronically controlled throttle system and the engine control system to exchange information and control the throttle in collaboration with each other.
For example, in the throttle full close position learning, all that is required is simply to operate the throttle valve until it makes contact with a stopper provided in its close direction, and it is not necessary for the engine to be rotating. In view of safety, it is rather preferable for the engine not working, thereby suppressing fuel injection and the engine should be stopped. In the full open learning, it is necessary for the engine to be controlled not to rotate. Further, in case a throttle opening is to be set up from a position of the acceleration pedal, it is necessary for the electronically controlled throttle system to inform a present position of the acceleration pedal to the engine control system such that the engine control system executes its engine control appropriately in response to the information.
Conventionally, in such a case as above, the electronically controlled throttle system and the engine control system are operated in synchronism with each other, and when the electronically controlled throttle system executes an operation that does not need engine speed, the engine control system is caused to take a measure to stop the engine operation. As a method for synchronizing therebetween, such methods have been utilized as one for taking a necessary step by exchanging contents of operation via a communication line therebetween, or one for monitoring a signal level of its ignition key and synchronizing at a period of timing of a change thereof.
However, as for the electronically controlled throttle system, it is more advantageous to be treated as a one unit and to minimize a relation with other systems, more specifically, interdependency with other systems, because a burden for newly incorporating the electronically controlled throttle system is substantially reduced. However, it should be noted that as described above, there is the case in which the electronically controlled throttle system depends on the behavior of the engine that is controlled by the engine control system.
An object of the present invention is to reduce an interdependency between the electronically controlled throttle system and the engine control system and improve a system reliability.
An electronically controlled throttle system of the invention monitors behaviors of an engine that is a target of direct control of an engine control system by means of an engine behavior monitor, and executes a fail-safe processing when a predetermined condition is not satisfied. An example of the engine behavior monitor is an engine speed monitor.
More specifically, when the electronically controlled throttle system of the invention controls its throttle independently of the engine control system, monitors engine behaviors using the engine behavior monitor, and if a predetermined condition is not satisfied, executes a fail-safe processing. For example, in the case in which the engine is controlled not to rotate in the step of the full open learning, when the engine behavior monitor that monitors engine speed indicates a value in excess of a predetermined speed, an engine control abnormality is judged to have occurred, and the electronically controlled throttle system terminates the full open learning operation abnormally. An advantage for allowing the electronically controlled throttle system also to monitor the engine behavior in addition to the monitoring and controlling by the engine control system resides in starting the fail-safe processing as quickly as possible and contributing to the improvement in the system reliability.
Because the full close learning or the full open learning are operations that do not require engine operation, there may be a case in which the electronically controlled throttle system and the engine control system are desired to be separated. Even in a state they are separated, in a method in which the electronically controlled throttle system is allowed to monitor the engine behavior, the electronically controlled throttle system is ensured to detect abnormality in the engine behavior and proceed to execute its fail-safe operation.